I don't think I've said anything particularly negative about referendums per se. It depends on what you want out of a referendum. One of the lessons I wanted to try to draw out of the New Zealand case is that the referendums—and they actually had two of them—were part of a larger process. They came at different times, so the debate in New Zealand went on for a long time.
Now whether it would have been different with or without referendums is hard to say; it's a counterfactual we can't really test. However, a referendum could fit in somewhere.
I think the model that's been proven not to work—and not just on this issue, but on other kinds of constitutional or quasi-constitutional issues as well—is where a small group behind closed doors comes up with a proposal then tosses it out there for the people to vote on, and in a three- or four-week campaign it's usually possible to pretty much put an end to it.